Idiotype network responses to murine immunoglobulin G3 anti-carbohydrate antibodies.

Two murine monoclonal antibodies, 8A6 and 8C2, were generated against the carbohydrate moiety of tumor-associated disialoganglioside. Both of the antibodies were of the immunoglobulin G3 (IgG3), K isotype subclass. One of these antibodies (8A6) was used as a network immunogen for the generation of anti-idiotype antibodies. Two AB2 anti-idiotype antibodies were identified. One AB2 (12E5) was subsequently shown to recognize a linear epitope of the 8A6 kappa light chain. The second AB2 (9H8), recognizes a conformational epitope which is dependent on the maintenance of the tertiary structure of the idiotype. Both anti-idiotypes were injected into (syngeneic) mice and (xenogeneic) rabbits to evaluate their effectiveness as "network" antigens in promoting AB3 and anti-carbohydrate AB1' responses. AB3 populations from both syngeneic and xenogeneic hosts were found to be idiotype-specific, yet were unable to produce a measurable subpopulation of anti-tumor (AB1'). These studies suggest that IgG3 isotypes may not be suitable idiotype templates for the mimicry of carbohydrate epitopes.